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Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]7 <title>LLVM 2.4 Release Notes</title>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]8</head>
9<body>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]10
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]11<div class="doc_title">LLVM 2.4 Release Notes</div>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]12
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]13<ol>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]14 <li><a href="#intro">Introduction</a></li>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]15 <li><a href="#subproj">Sub-project Status Update</a></li>
16 <li><a href="#whatsnew">What's New in LLVM?</a></li>
Chris Lattner4b538b92004-04-30 22:17:12 +0000[diff] [blame]17 <li><a href="GettingStarted.html">Installation Instructions</a></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]18 <li><a href="#portability">Portability and Supported Platforms</a></li>
Dan Gohman44aa9212008-10-14 16:23:02 +0000[diff] [blame]19 <li><a href="#knownproblems">Known Problems</a></li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]20 <li><a href="#additionalinfo">Additional Information</a></li>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]21</ol>
22
Chris Lattner7911ce22004-05-23 21:07:27 +0000[diff] [blame]23<div class="doc_author">
Dan Gohman44aa9212008-10-14 16:23:02 +0000[diff] [blame]24 <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]25</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]26
27<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]28<div class="doc_section">
29 <a name="intro">Introduction</a>
30</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]31<!-- *********************************************************************** -->
32
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]33<div class="doc_text">
34
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]35<p>This document contains the release notes for the LLVM Compiler
36Infrastructure, release 2.4. Here we describe the status of LLVM, including
37major improvements from the previous release and significant known problems.
38All LLVM releases may be downloaded from the <a
39href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]40
Chris Lattner7506b1d2004-12-07 08:04:13 +0000[diff] [blame]41<p>For more information about LLVM, including information about the latest
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]42release, please check out the <a href="http://llvm.org/">main LLVM
Chris Lattner47ad72c2003-10-07 21:38:31 +0000[diff] [blame]43web site</a>. If you have questions or comments, the <a
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]44href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
45List</a> is a good place to send them.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]46
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]47<p>Note that if you are reading this file from a Subversion checkout or the
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]48main LLVM web page, this document applies to the <i>next</i> release, not the
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]49current one. To see the release notes for a specific release, please see the
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]50<a href="http://llvm.org/releases/">releases page</a>.</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]51
52</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]53
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]54<!-- Unfinished features in 2.4:
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]55 Machine LICM
56 Machine Sinking
57 LegalizeDAGTypes
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]58 llc -enable-value-prop, propagation of value info (sign/zero ext info) from
59 one MBB to another
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]60 -->
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]61
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]62 <!-- for announcement email:
63 mention dev mtg
Chris Lattnercdb0e4c2008-10-12 22:57:58 +0000[diff] [blame]64 Xcode 3.1 and 3.1.1.
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]65 -->
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]66
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]67<!-- *********************************************************************** -->
68<div class="doc_section">
69 <a name="subproj">Sub-project Status Update</a>
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]70</div>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]71<!-- *********************************************************************** -->
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]72
73<div class="doc_text">
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]74<p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]75The LLVM 2.4 distribution currently consists of code from the core LLVM
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000[diff] [blame]76repository (which roughly includes the LLVM optimizers, code generators and
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]77supporting tools) and the llvm-gcc repository. In addition to this code, the
78LLVM Project includes other sub-projects that are in development. The two which
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]79are the most actively developed are the <a href="#clang">Clang Project</a> and
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]80the <a href="#vmkit">VMKit Project</a>.
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]81</p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]82
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]83</div>
84
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]85
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]86<!--=========================================================================-->
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]87<div class="doc_subsection">
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000[diff] [blame]88<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]89</div>
90
91<div class="doc_text">
92
93<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
94a set of new 'LLVM native' front-end technologies for the LLVM optimizer
95and code generator. Clang is continuing to make major strides forward in all
96areas. Its C and Objective-C parsing support is very solid, and the code
97generation support is far enough along to build many C applications. While not
98yet production quality, it is progressing very nicely. In addition, C++
99front-end work has started to make significant progress.</p>
100
Daniel Dunbar13739432008-10-14 23:25:09 +0000[diff] [blame]101Clang, in conjunction with the <tt>ccc</tt> driver, is now usable as a
102replacement for gcc for building some small- to medium-sized C applications.
103Additionally, Clang now has code generation support for Objective-C on Mac OS X
104platform. Major highlights include:
105<ul>
106 <li> Clang/ccc pass almost all of the LLVM test suite on Mac OS X and Linux
107on the 32-bit x86 architecture. This includes significant C
108applications such as <a href="http://www.sqlite.org">sqlite3</a>,
109<a href="http://www.lua.org">lua</a>, and
110<a href="http://www.clamav.net">Clam AntiVirus</a>.
111
112 <li> Clang can build the majority of Objective-C examples shipped with the
113Mac OS X Developer Tools.
114</ul>
115
116Clang code generation still needs considerable testing and development, however.
117Some areas under active development include:
118<ul>
119 <li> Improved support for C and Objective-C features, for example
Gabor Greif804ffb62008-10-15 10:29:51 +0000[diff] [blame]120 variable-length arrays, va_arg, exception handling (Obj-C), and garbage
Daniel Dunbar13739432008-10-14 23:25:09 +0000[diff] [blame]121 collection (Obj-C).
122 <li> ABI compatibility, especially for platforms other than 32-bit x86.
123</ul>
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]124
Chris Lattnerfb97b2d2008-10-13 18:11:54 +0000[diff] [blame]125</div>
126
127<!--=========================================================================-->
128<div class="doc_subsection">
129<a name="clangsa">Clang Static Analyzer</a>
130</div>
131
132<div class="doc_text">
133
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]134<p>The Clang project also includes an early stage static source code analysis
135tool for <a href="http://clang.llvm.org/StaticAnalysis.html">automatically
136finding bugs</a> in C and Objective-C programs. The tool performs a growing set
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]137of checks to find bugs that occur on a specific path within a program. Examples
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]138of bugs the tool finds include logic errors such as null dereferences,
139violations of various API rules, dead code, and potential memory leaks in
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]140Objective-C programs. Since its inception, public feedback on the tool has been
141extremely positive, and conservative estimates put the number of real bugs it
142has found in industrial-quality software on the order of thousands.</p>
Chris Lattnercc042612008-10-14 00:52:49 +0000[diff] [blame]143
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]144<p>The tool also provides a simple web GUI to inspect potential bugs found by
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]145the tool. While still early in development, the GUI illustrates some of the key
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]146features of Clang: accurate source location information, which is used by the
147GUI to highlight specific code expressions that relate to a bug (including those
148that span multiple lines) and built-in knowledge of macros, which is used to
149perform inline expansion of macros within the GUI itself.</p>
150
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]151<p>The set of checks performed by the static analyzer is gradually expanding,
152and
Ted Kremenek3c3ec0c2008-10-14 05:14:21 +0000[diff] [blame]153future plans for the tool include full source-level inter-procedural analysis
154and deeper checks such as buffer overrun detection. There are many opportunities
155to extend and enhance the static analyzer, and anyone interested in working on
156this project is encouraged to get involved!</p>
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]157
158</div>
159
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]160<!--=========================================================================-->
161<div class="doc_subsection">
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]162<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]163</div>
164
165<div class="doc_text">
166<p>
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]167The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]168a JVM and a CLI Virtual Machines (Microsoft .NET is an
169implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
170
Nicolas Geoffray56d313d2008-10-15 20:25:04 +0000[diff] [blame^]171<p>Following LLVM 2.4, VMKit has its first release 0.24 that you can find on its
172<a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
173bug fixes, cleanup and new features. The major changes are:</p>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]174
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]175<ul>
176
Nicolas Geoffray56d313d2008-10-15 20:25:04 +0000[diff] [blame^]177<li> Support for generics in the .Net virtual machine.
Gabor Greif804ffb62008-10-15 10:29:51 +0000[diff] [blame]178<li> Initial support for the Mono class libraries.
179<li> Support for MacOSX/x86, following LLVM's support for exceptions in
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]180JIT on MacOSX/x86.
Gabor Greif804ffb62008-10-15 10:29:51 +0000[diff] [blame]181<li> A new vmkit driver: a program to run java or .net applications. The
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]182driver supports llvm command line arguments including the new "-fast" option.
Gabor Greif804ffb62008-10-15 10:29:51 +0000[diff] [blame]183<li> A new memory allocation scheme in the JVM that makes unloading a
184class loader very fast.
185<li> VMKit now follows the LLVM Makefile machinery.
Nicolas Geoffray99a4d302008-10-14 19:23:04 +0000[diff] [blame]186
187</ul>
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]188</div>
189
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]190
191<!-- *********************************************************************** -->
192<div class="doc_section">
Chris Lattner96a445e2008-10-13 18:01:01 +0000[diff] [blame]193 <a name="whatsnew">What's New in LLVM?</a>
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]194</div>
195<!-- *********************************************************************** -->
196
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]197<div class="doc_text">
198
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]199<p>This release includes a huge number of bug fixes, performance tweaks and
200minor improvements. Some of the major improvements and new features are listed
201in this section.
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]202</p>
203</div>
204
Chris Lattner8348b472008-06-08 21:58:17 +0000[diff] [blame]205<!--=========================================================================-->
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]206<div class="doc_subsection">
Chris Lattner252b83d2008-02-06 18:00:06 +0000[diff] [blame]207<a name="majorfeatures">Major New Features</a>
208</div>
209
210<div class="doc_text">
211
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]212<p>LLVM 2.4 includes several major new capabilities:</p>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]213
214<ul>
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]215<li><p>The most visible end-user change in LLVM 2.4 is that it includes many
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]216optimizations and changes to make -O0 compile times much faster. You should see
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]217improvements on the order of 30% (or more) faster than LLVM 2.3. There are many
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]218pieces to this change, described in more detail below. The speedups and new
219components can also be used for JIT compilers that want fast compilation as
220well.</p></li>
Chris Lattner857fb132008-10-11 18:18:28 +0000[diff] [blame]221
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]222<li><p>The biggest change to the LLVM IR is that Multiple Return Values (which
223were introduced in LLVM 2.3) have been generalized to full support for "First
224Class Aggregate" values in LLVM 2.4. This means that LLVM IR supports using
225structs and arrays as values in a function. This capability is mostly useful
226for front-end authors, who prefer to treat things like complex numbers, simple
227tuples, dope vectors, etc as Value*'s instead of as a tuple of Value*'s or as
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]228memory values. Bitcode files from LLVM 2.3 will automatically migrate to the
229general representation.</p></li>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]230
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]231<li><p>LLVM 2.4 also includes an initial port for the PIC16 microprocessor. This
Duncan Sands9ba23792008-10-14 07:06:37 +0000[diff] [blame]232is the LLVM target that only has support for 8 bit registers, and a number of
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]233other crazy constraints. While the port is still in early development stages,
234it shows some interesting things you can do with LLVM.</p></li>
Chris Lattnerbc5786b2008-06-05 06:57:39 +0000[diff] [blame]235
Chris Lattner8170c102008-02-10 08:18:42 +0000[diff] [blame]236</ul>
237
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]238</div>
239
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]240
241<!--=========================================================================-->
242<div class="doc_subsection">
Chris Lattnerea34f642008-06-08 21:34:41 +0000[diff] [blame]243<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]244</div>
245
246<div class="doc_text">
247
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]248<p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
249front-ends and driver with the LLVM optimizer and code generator. It currently
250includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]251
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]252<ul>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]253<li>LLVM 2.4 supports the full set of atomic <tt>__sync_*</tt> builtins. LLVM
2542.3 only supported those used by OpenMP, but 2.4 supports them all. While
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]255llvm-gcc supports all of these builtins, note that not all targets do. X86
256support them all in both 32-bit and 64-bit mode and PowerPC supports them all
257except for the 64-bit operations when in 32-bit mode.</li>
Chris Lattnerf8e0b4e2008-06-08 22:59:35 +0000[diff] [blame]258
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]259<li>llvm-gcc now supports an <tt>-flimited-precision</tt> option, which tells
260the compiler that it is ok to use low-precision approximations of certain libm
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]261functions (like tan, log, etc). This allows you to get high performance if you
262only need (say) 14-bits of precision.</li>
263
264<li>llvm-gcc now supports a C language extension known as "<a
265href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-August/002670.html">Blocks
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]266</a>". This feature is similar to nested functions and closures, but does not
Chris Lattnerb82eb062008-10-13 20:47:20 +0000[diff] [blame]267require stack trampolines (with most ABIs) and supports returning closures
268from functions that define them. Note that actually <em>using</em> Blocks
269requires a small runtime that is not included with llvm-gcc.</li>
270
271<li>llvm-gcc now supports a new <tt>-flto</tt> option. On systems that support
272transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and
273later) this allows the use of LTO with other optimization levels like -Os.
274Previously, LTO could only be used with -O4, which implied optimizations in
275-O3 that can increase code size.</li>
Gabor Greifa3bd11d2008-06-09 06:06:18 +0000[diff] [blame]276</ul>
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]277
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]278</div>
279
280
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]281<!--=========================================================================-->
282<div class="doc_subsection">
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]283<a name="coreimprovements">LLVM Core Improvements</a>
284</div>
285
286<div class="doc_text">
287<p>New features include:
288</p>
289
Chris Lattner791f77b2008-06-05 06:25:56 +0000[diff] [blame]290<ul>
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]291<li>A major change to the <tt>Use</tt> class landed, which shrank it by 25%. Since
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]292this is a pervasive part of the LLVM, it ended up reducing the memory use of
293LLVM IR in general by 15% for most programs.</li>
294
295<li>Values with no names are now pretty printed by <tt>llvm-dis</tt> more
296nicely. They now print as "<tt>%3 = add i32 %A, 4</tt>" instead of
297"<tt>add i32 %A, 4 ; &lt;i32&gt;:3</tt>", which makes it much easier to read.
298</li>
299
300<li>LLVM 2.4 includes some changes for better vector support. First, the shift
301operations (<tt>shl</tt>, <tt>ashr</tt>, <tt>lshr</tt>) now all support vectors
302and do an element-by-element shift (shifts of the whole vector can be
303accomplished by bitcasting the vector to &lt;1 x i128&gt; for example). Second,
Chris Lattnercc042612008-10-14 00:52:49 +0000[diff] [blame]304there is initial support in development for vector comparisons with the
305<a href="LangRef.html#i_fcmp">fcmp</a>/<a href="LangRef.html#i_icmp">icmp</a>
306instructions. These instructions compare two vectors and return a vector of
307i1's for each result. Note that there is very little codegen support available
308for any of these IR features though.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]309
310<li>A new <tt>DebugInfoBuilder</tt> class is available, which makes it much
311easier for front-ends to create debug info descriptors, similar to the way that
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]312<tt>IRBuilder</tt> makes it easier to create LLVM IR.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]313
Dan Gohman1bbddce2008-10-14 16:13:59 +0000[diff] [blame]314<li>The <tt>IRBuilder</tt> class is now parameterized by a class responsible
Gabor Greiffa933f82008-10-14 11:00:32 +0000[diff] [blame]315for constant folding. The default <tt>ConstantFolder</tt> class does target independent
316constant folding. The <tt>NoFolder</tt> class does no constant folding at all, which is
317useful when learning how LLVM works. The <tt>TargetFolder</tt> class folds the most,
Duncan Sands9ba23792008-10-14 07:06:37 +0000[diff] [blame]318doing target dependent constant folding.</li>
319
320<li>LLVM now supports "function attributes", which allows us to separate return
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]321value attributes from function attributes. LLVM now supports attributes on a
322function itself, a return value, and its parameters. New supported function
323attributes include noinline/alwaysinline and the "opt-size" flag which says the
324function should be optimized for code size.</li>
325
Chris Lattnercce6d4b2008-10-12 18:30:33 +0000[diff] [blame]326<li>LLVM IR now directly represents "common" linkage, instead of
327 representing it as a form of weak linkage.</li>
Chris Lattner7752d1a2008-10-13 20:59:32 +0000[diff] [blame]328
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]329</ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]330
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]331</div>
332
333<!--=========================================================================-->
334<div class="doc_subsection">
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]335<a name="optimizer">Optimizer Improvements</a>
336</div>
337
338<div class="doc_text">
339
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]340<p>In addition to a huge array of bug fixes and minor performance tweaks, this
341release includes a few major enhancements and additions to the optimizers:</p>
Chris Lattneracce85d2008-02-10 07:46:44 +0000[diff] [blame]342
343<ul>
344
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]345<li>The Global Value Numbering (GVN) pass now does local Partial Redundancy
346Elimination (PRE) to eliminate some partially redundant expressions in cases
347where doing so won't grow code size.</li>
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]348
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]349<li>LLVM 2.4 includes a new loop deletion pass (which removes output-free
350provably-finite loops) and a rewritten Aggressive Dead Code Elimination (ADCE)
351pass that no longer uses control dependence information. These changes speed up
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]352the optimizer and also prevent it from deleting output-free infinite
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]353loops.</li>
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]354
Duncan Sands1050d732008-10-13 18:42:43 +0000[diff] [blame]355<li>The new AddReadAttrs pass works out which functions are read-only or
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]356read-none (these correspond to 'pure' and 'const' in GCC) and marks them
Duncan Sands1050d732008-10-13 18:42:43 +0000[diff] [blame]357with the appropriate attribute.</li>
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]358
359<li>LLVM 2.4 now includes a new SparsePropagation framework, which makes it
360trivial to build lattice-based dataflow solvers that operate over LLVM IR. Using
361this interface means that you just define objects to represent your lattice
362values and the transfer functions that operate on them. It handles the
363mechanics of worklist processing, liveness tracking, handling PHI nodes,
364etc.</li>
365
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]366<li>The Loop Strength Reduction and induction variable optimization passes have
367several improvements to avoid inserting MAX expressions, to optimize simple
368floating point induction variables and to analyze trip counts of more
369loops.</li>
370
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]371<li>Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were
372pulled out of the Instruction Combining pass and put into a new
373<tt>ValueTracking.h</tt> header, where they can be reused by other passes.</li>
374
375<li>The tail duplication pass has been removed from the standard optimizer
376sequence used by llvm-gcc. This pass still exists, but the benefits it once
377provided are now achieved by other passes.</li>
378
Chris Lattner0b832202008-06-08 02:45:07 +0000[diff] [blame]379</ul>
380
381</div>
382
383<!--=========================================================================-->
384<div class="doc_subsection">
385<a name="codegen">Code Generator Improvements</a>
386</div>
387
388<div class="doc_text">
389
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]390<p>We have put a significant amount of work into the code generator infrastructure,
Chris Lattner0b832202008-06-08 02:45:07 +0000[diff] [blame]391which allows us to implement more aggressive algorithms and make it run
392faster:</p>
393
394<ul>
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]395<li>The target-independent code generator supports (and the X86 backend
396 currently implements) a new interface for "fast" instruction selection. This
397 interface is optimized to produce code as quickly as possible, sacrificing
398 code quality to do it. This is used by default at -O0 or when using
399 "llc -fast" on X86. It is straight-forward to add support for
400 other targets if faster -O0 compilation is desired.</li>
401
402<li>In addition to the new 'fast' instruction selection path, many existing
403 pieces of the code generator have been optimized in significant ways.
404 SelectionDAG's are now pool allocated and use better algorithms in many
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]405 places, the ".s" file printers now use <tt>raw_ostream</tt> to emit text much faster,
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]406 etc. The end result of these improvements is that the compiler also takes
407 substantially less time to generate code that is just as good (and often
408 better) than before.</li>
409
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]410<li>Each target has been split to separate the ".s" file printing logic from the
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]411 rest of the target. This enables JIT compilers that don't link in the
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]412 (somewhat large) code and data tables used for printing a ".s" file.</li>
Chris Lattnerf3013872008-10-13 21:50:36 +0000[diff] [blame]413
414<li>The code generator now includes a "stack slot coloring" pass, which packs
415 together individual spilled values into common stack slots. This reduces
416 the size of stack frames with many spills, which tends to increase L1 cache
417 effectiveness.</li>
418
419<li>Various pieces of the register allocator (e.g. the coalescer and two-address
420 operation elimination pass) now know how to rematerialize trivial operations
421 to avoid copies and include several other optimizations.</li>
422
423<li>The <a href="CodeGenerator.html#selectiondag_process">graphs</a> produced by
424 the <tt>llc -view-*-dags</tt> options are now significantly prettier and
425 easier to read.</li>
426
427<li>LLVM 2.4 includes a new register allocator based on Partitioned Boolean
428 Quadratic Programming (PBQP). This register allocator is still in
429 development, but is very simple and clean.</li>
Chris Lattner0b832202008-06-08 02:45:07 +0000[diff] [blame]430
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]431</ul>
432
433</div>
434
435
436<!--=========================================================================-->
437<div class="doc_subsection">
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]438<a name="targetspecific">Target Specific Improvements</a>
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]439</div>
Chris Lattner60893e52007-05-18 06:33:02 +0000[diff] [blame]440
Chris Lattner738bd302006-04-18 06:32:08 +0000[diff] [blame]441<div class="doc_text">
Chris Lattnerf304ffc2008-02-10 08:17:19 +0000[diff] [blame]442<p>New target-specific features include:
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]443</p>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]444
445<ul>
Chris Lattner547a3912008-10-12 19:47:48 +0000[diff] [blame]446<li>Exception handling is supported by default on Linux/x86-64.</li>
Duncan Sandsbbf379a2008-10-13 17:32:15 +0000[diff] [blame]447<li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li>
Chris Lattnerc702d162008-10-14 06:02:29 +0000[diff] [blame]448<li>@llvm.frameaddress now supports getting the frame address of stack frames
449 &gt; 0 on x86/x86-64.</li>
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]450<li>MIPS floating point support? [BRUNO]</li>
451<li>The PowerPC backend now supports trampolines.</li>
Chris Lattner77d29b12008-06-05 08:02:49 +0000[diff] [blame]452</ul>
Chris Lattner77d29b12008-06-05 08:02:49 +0000[diff] [blame]453
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]454</div>
Chris Lattner77d29b12008-06-05 08:02:49 +0000[diff] [blame]455
456
457<!--=========================================================================-->
458<div class="doc_subsection">
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]459<a name="otherimprovements">Other Improvements</a>
460</div>
461
462<div class="doc_text">
463<p>New features include:
464</p>
465
466<ul>
Mikhail Glushenkov49feb452008-10-13 02:46:01 +0000[diff] [blame]467<li><tt>llvmc2</tt> (the generic compiler driver) gained plugin
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]468 support. It is now easier to experiment with <tt>llvmc2</tt> and
469 build your own tools based on it.</li>
470
471<li>LLVM 2.4 includes a number of new generic algorithms and data structures,
Dan Gohmanbd9f9af2008-10-14 15:14:55 +0000[diff] [blame]472 include a scoped hash table, 'immutable' data structures, a simple
473 free-list manager, and a <tt>raw_ostream</tt> class.
474 The <tt>raw_ostream</tt> class and
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]475 <tt>format</tt> allow for efficient file output, and various pieces of LLVM
476 have switched over to use it. The eventual goal is to eliminate
477 std::ostream in favor of it.</li>
478
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]479</ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]480
Chris Lattner84977642007-09-21 03:54:09 +0000[diff] [blame]481</div>
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000[diff] [blame]482
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]483<!--=========================================================================-->
484<div class="doc_subsection">
485<a name="changes">Major Changes and Removed Features</a>
486</div>
487
488<div class="doc_text">
489
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]490<p>If you're already an LLVM user or developer with out-of-tree changes based
491on LLVM 2.3, this section lists some "gotchas" that you may run into upgrading
492from the previous release.</p>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]493
494<ul>
495
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]496<li>The LLVM IR generated by llvm-gcc no longer names all instructions. This
497 makes it run faster, but may be more confusing to some people. If you
498 prefer to have names, the '<tt>opt -instnamer</tt>' pass will add names to
499 all instructions.</li>
500
501<li>The LoadVN and GCSE passes have been removed from the tree. They are
502 obsolete and have been replaced with the GVN and MemoryDependence passes.
503 </li>
504</ul>
505
506
507<p>In addition, many APIs have changed in this release. Some of the major LLVM
508API changes are:</p>
509
510<ul>
511
Devang Patelb34dd132008-10-14 20:03:43 +0000[diff] [blame]512<li>Now, function attributes and return value attributes are managed
Gabor Greif3bd3a262008-10-15 10:47:24 +0000[diff] [blame]513separately. Interface exported by <tt>ParameterAttributes.h</tt> header is now
Devang Patelb34dd132008-10-14 20:03:43 +0000[diff] [blame]514experted by <tt>Attributes.h</tt> header. The new attributes interface changes are:
515<ul>
516<li><tt>getParamAttrs</tt> method is now replaced by
517<tt>getParamAttributes</tt>, <tt>getRetAttributes</tt> and
518<tt>getFnAttributes</tt> methods.</li>
519<li> Return value attributes are stored at index 0. Function attributes are
520stored at index ~0U. Parameter attributes are stored at index that matches
521parameter number.</li>
522<li> <tt>ParamAttr</tt> namespace is now renamed as <tt>Attribute</tt>.</li>
Gabor Greif804ffb62008-10-15 10:29:51 +0000[diff] [blame]523<li> The name of the class that manages reference count of opaque
Devang Patelb34dd132008-10-14 20:03:43 +0000[diff] [blame]524attributes is changed from <tt>PAListPtr</tt> to <tt>AttrListPtr</tt>.</li>
525<li> <tt>ParamAttrsWithIndex</tt> is now renamed as <tt>AttributeWithIndex</tt>.
526</li>
527</ul>
528</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]529
530<li>The <tt>DbgStopPointInst</tt> methods <tt>getDirectory</tt> and
531<tt>getFileName</tt> now return <tt>Value*</tt> instead of strings. These can be
532converted to strings using <tt>llvm::GetConstantStringInfo</tt> defined via
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]533"<tt>llvm/Analysis/ValueTracking.h</tt>".</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]534
Chris Lattnereeb4da02008-10-13 22:06:31 +0000[diff] [blame]535<li>The APIs to create various instructions have changed from lower case
536 "create" methods to upper case "Create" methods (e.g.
537 <tt>BinaryOperator::create</tt>). LLVM 2.4 includes both cases, but the
538 lower case ones are removed in mainline, please migrate.</li>
539
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]540<li>Various header files like "<tt>llvm/ADT/iterator</tt>" were given a ".h" suffix.
541 Change your code to #include "<tt>llvm/ADT/iterator.h</tt>" instead.</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]542
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]543<li>In the code generator, many <tt>MachineOperand</tt> predicates were renamed to be
Chris Lattnerf1796b62008-10-14 06:37:11 +0000[diff] [blame]544 shorter (e.g. <tt>isFrameIndex()</tt> -&gt; <tt>isFI()</tt>),
545 <tt>SDOperand</tt> was renamed to <tt>SDValue</tt> (and the "<tt>Val</tt>"
546 member was changed to be the <tt>getNode()</tt> accessor), and the
547 <tt>MVT::ValueType</tt> enum has been replaced with an "<tt>MVT</tt>"
Dan Gohman9aeea5b2008-10-14 17:06:44 +0000[diff] [blame]548 struct. The <tt>getSignExtended</tt> and <tt>getValue</tt> methods in the
549 ConstantSDNode class were renamed to <tt>getSExtValue</tt> and
550 <tt>getZExtValue</tt> respectively, to be more consistent with
551 the <tt>ConstantInt</tt> class.</li>
Chris Lattnerf6662f92008-10-13 17:57:36 +0000[diff] [blame]552</ul>
553
554</div>
555
556
557
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]558<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]559<div class="doc_section">
560 <a name="portability">Portability and Supported Platforms</a>
561</div>
Chris Lattner19092612003-10-02 16:38:05 +0000[diff] [blame]562<!-- *********************************************************************** -->
563
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]564<div class="doc_text">
565
John Criswell0b5b5e92004-12-08 20:35:47 +0000[diff] [blame]566<p>LLVM is known to work on the following platforms:</p>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000[diff] [blame]567
568<ul>
Mikhail Glushenkovea65d7d2008-10-13 02:08:34 +0000[diff] [blame]569<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
Reid Spencer00812e22005-05-17 02:47:27 +0000[diff] [blame]570 (and probably other unix-like systems).</li>
Chris Lattner000c73b2008-02-06 06:30:34 +0000[diff] [blame]571<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]572 64-bit modes.</li>
Chris Lattner252b83d2008-02-06 18:00:06 +0000[diff] [blame]573<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]574<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
575 support is available for native builds with Visual C++).</li>
Gabor Greif96a89c72008-06-05 18:39:01 +0000[diff] [blame]576<li>Sun UltraSPARC workstations running Solaris 10.</li>
John Criswell9321fa82005-05-13 20:28:15 +0000[diff] [blame]577<li>Alpha-based machines running Debian GNU/Linux.</li>
Gabor Greif96a89c72008-06-05 18:39:01 +0000[diff] [blame]578<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
Chris Lattner4654bdb2004-06-01 18:22:41 +0000[diff] [blame]579</ul>
580
Chris Lattnerbc5786b2008-06-05 06:57:39 +0000[diff] [blame]581<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
Brian Gaekeb0fd7612004-05-09 05:28:35 +0000[diff] [blame]582to the machine and operating system on which it is built. However, minor
583porting may be required to get LLVM to work on new platforms. We welcome your
584portability patches and reports of successful builds or error messages.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]585
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]586</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]587
588<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]589<div class="doc_section">
590 <a name="knownproblems">Known Problems</a>
591</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]592<!-- *********************************************************************** -->
593
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]594<div class="doc_text">
595
596<p>This section contains all known problems with the LLVM system, listed by
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]597component. As new problems are discovered, they will be added to these
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]598sections. If you run into a problem, please check the <a
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]599href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]600there isn't already one.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]601
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]602</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]603
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]604<!-- ======================================================================= -->
605<div class="doc_subsection">
606 <a name="experimental">Experimental features included with this release</a>
607</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]608
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]609<div class="doc_text">
610
Misha Brukman6df9e2c2004-05-12 21:46:05 +0000[diff] [blame]611<p>The following components of this LLVM release are either untested, known to
612be broken or unreliable, or are in early development. These components should
613not be relied on, and bugs should not be filed against them, but they may be
614useful to some people. In particular, if you would like to work on one of these
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]615components, please contact us on the <a
616href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]617
618<ul>
Gabor Greifa8b84902008-10-14 11:31:14 +0000[diff] [blame]619<li>The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]620<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
Chris Lattner000c73b2008-02-06 06:30:34 +0000[diff] [blame]621 value for this option.</li>
Chris Lattnerf5ee1702004-03-14 02:03:02 +0000[diff] [blame]622</ul>
623
624</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]625
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]626<!-- ======================================================================= -->
627<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]628 <a name="x86-be">Known problems with the X86 back-end</a>
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]629</div>
630
631<div class="doc_text">
632
633<ul>
Anton Korobeynikova6094be2008-06-08 10:24:13 +0000[diff] [blame]634 <li>The X86 backend does not yet support
635 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
636 floating point stack</a>. It supports the 'f' and 't' constraints, but not
637 'u'.</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000[diff] [blame]638 <li>The X86 backend generates inefficient floating point code when configured
639 to generate code for systems that don't have SSE2.</li>
Duncan Sands47eff2b2008-06-08 19:38:43 +0000[diff] [blame]640 <li>Win64 code generation wasn't widely tested. Everything should work, but we
Anton Korobeynikova6094be2008-06-08 10:24:13 +0000[diff] [blame]641 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
642 currently due
643 to <a href="http://llvm.org/PR2255">several</a>
Chris Lattner04af7cb2008-06-08 23:12:47 +0000[diff] [blame]644 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
645 'u' inline assembly constraint and X87 floating point inline assembly.</li>
Dan Gohman8207ba92008-06-08 23:05:11 +0000[diff] [blame]646 <li>The X86-64 backend does not yet support the LLVM IR instruction
647 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
648 argument constructs on X86-64 by lowering them manually.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]649</ul>
650
651</div>
652
653<!-- ======================================================================= -->
654<div class="doc_subsection">
655 <a name="ppc-be">Known problems with the PowerPC back-end</a>
656</div>
657
658<div class="doc_text">
659
660<ul>
Nicolas Geoffraye4285dc2007-05-15 09:21:28 +0000[diff] [blame]661<li>The Linux PPC32/ABI support needs testing for the interpreter and static
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]662compilation, and lacks support for debug information.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]663</ul>
664
665</div>
666
667<!-- ======================================================================= -->
668<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]669 <a name="arm-be">Known problems with the ARM back-end</a>
670</div>
671
672<div class="doc_text">
673
674<ul>
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]675<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
Duncan Sandsc90d68b2007-09-26 15:59:54 +0000[diff] [blame]676processors, thumb programs can crash or produce wrong
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]677results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]678<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
679</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000[diff] [blame]680<li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly
681 execute
Chris Lattner57a460e2007-05-23 04:39:32 +0000[diff] [blame]682programs compiled with LLVM. Please use more recent versions of QEMU.</li>
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]683</ul>
684
685</div>
686
687<!-- ======================================================================= -->
688<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]689 <a name="sparc-be">Known problems with the SPARC back-end</a>
690</div>
691
692<div class="doc_text">
693
694<ul>
695<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
696 support the 64-bit SPARC ABI (-m64).</li>
697</ul>
698
699</div>
700
701<!-- ======================================================================= -->
702<div class="doc_subsection">
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]703 <a name="alpha-be">Known problems with the Alpha back-end</a>
704</div>
705
706<div class="doc_text">
707
708<ul>
709
710<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
711appropriate nops inserted to ensure restartability.</li>
712
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]713</ul>
714</div>
715
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]716<!-- ======================================================================= -->
717<div class="doc_subsection">
718 <a name="ia64-be">Known problems with the IA64 back-end</a>
719</div>
720
721<div class="doc_text">
722
723<ul>
Chris Lattner04af7cb2008-06-08 23:12:47 +0000[diff] [blame]724<li>The Itanium backend is highly experimental, and has a number of known
725 issues. We are looking for a maintainer for the Itanium backend. If you
Gabor Greif3bd3a262008-10-15 10:47:24 +0000[diff] [blame]726 are interested, please contact the LLVMdev mailing list.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]727</ul>
728
729</div>
730
731<!-- ======================================================================= -->
732<div class="doc_subsection">
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]733 <a name="c-be">Known problems with the C back-end</a>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]734</div>
735
736<div class="doc_text">
737
738<ul>
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]739<li><a href="http://llvm.org/PR802">The C backend has only basic support for
740 inline assembly code</a>.</li>
Chris Lattner725a0d82007-09-26 06:01:35 +0000[diff] [blame]741<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
742 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]743 C++ code compiled with llc or native compilers.</li>
Duncan Sandsf74c0cc2008-02-10 13:40:55 +0000[diff] [blame]744<li>The C backend does not support all exception handling constructs.</li>
Chris Lattner26299222006-11-18 07:51:14 +0000[diff] [blame]745</ul>
746
747</div>
John Criswellc0c186d2005-11-08 21:11:33 +0000[diff] [blame]748
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]749
750<!-- ======================================================================= -->
751<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]752 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]753</div>
Chris Lattner47588f92003-10-02 05:07:23 +0000[diff] [blame]754
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]755<div class="doc_text">
Chris Lattnerc5d658a2006-03-03 00:34:26 +0000[diff] [blame]756
Chris Lattner252b83d2008-02-06 18:00:06 +0000[diff] [blame]757<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
758Optimization</a> on most platforms "out-of-the-box". Please inquire on the
Gabor Greif3bd3a262008-10-15 10:47:24 +0000[diff] [blame]759LLVMdev mailing list if you are interested.</p>
Chris Lattnerd9ea0172006-08-08 17:27:28 +0000[diff] [blame]760
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]761<p>The only major language feature of GCC not supported by llvm-gcc is
762 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
763 are only supported on some targets. For example, trampolines are only
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]764 supported on some targets (these are used when you take the address of a
765 nested function).</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]766
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]767<p>If you run into GCC extensions which are not supported, please let us know.
768</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]769
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]770</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]771
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]772<!-- ======================================================================= -->
773<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]774 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]775</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]776
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]777<div class="doc_text">
778
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]779<p>The C++ front-end is considered to be fully
Chris Lattner7506b1d2004-12-07 08:04:13 +0000[diff] [blame]780tested and works for a number of non-trivial programs, including LLVM
Chris Lattnerf3e5bc62007-05-14 06:56:09 +0000[diff] [blame]781itself, Qt, Mozilla, etc.</p>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]782
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]783<ul>
Anton Korobeynikov0021fc12008-10-11 18:27:16 +0000[diff] [blame]784<li>Exception handling works well on the X86 and PowerPC targets. Currently
785 only linux and darwin targets are supported (both 32 and 64 bit).</li>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]786</ul>
Chris Lattnerfcc54b32003-10-07 22:14:37 +0000[diff] [blame]787
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]788</div>
789
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]790
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]791<!-- ======================================================================= -->
792<div class="doc_subsection">
Chris Lattner5733b272008-06-05 06:35:40 +0000[diff] [blame]793 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]794</div>
795
796<div class="doc_text">
797The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
798technology and problems should be expected.
799<ul>
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]800<li>The Ada front-end currently only builds on X86-32. This is mainly due
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]801to lack of trampoline support (pointers to nested functions) on other platforms,
Duncan Sands27aff872008-06-08 20:18:35 +0000[diff] [blame]802however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]803which does support trampolines.</li>
804<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
805Workaround: configure with --disable-bootstrap.</li>
Duncan Sands978bcee2008-10-13 17:27:23 +0000[diff] [blame]806<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
807and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
808(c380004 also fails with gcc-4.2 mainline).</li>
809<li>Some gcc specific Ada tests continue to crash the compiler.</li>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]810<li>The -E binder option (exception backtraces)
811<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
812crashing if an exception is raised. Workaround: do not use -E.</li>
813<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
814or finish at a non-byte offset</a> in a record. Workaround: do not pack records
815or use representation clauses that result in a field of a non-discrete type
816starting or finishing in the middle of a byte.</li>
Chris Lattnere6e1b352008-06-08 21:19:07 +0000[diff] [blame]817<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
818'main' as generated by the Ada binder to be invalid</a>.
819Workaround: hand edit the file to use pointers for <tt>argv</tt> and
820<tt>envp</tt> rather than integers.</li>
821<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
822ignored</a>.</li>
Chris Lattner2b659ef2008-02-12 06:29:45 +0000[diff] [blame]823</ul>
824</div>
825
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]826<!-- *********************************************************************** -->
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]827<div class="doc_section">
828 <a name="additionalinfo">Additional Information</a>
829</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]830<!-- *********************************************************************** -->
831
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]832<div class="doc_text">
833
Chris Lattner416db102005-05-16 17:13:10 +0000[diff] [blame]834<p>A wide variety of additional information is available on the <a
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000[diff] [blame]835href="http://llvm.org">LLVM web page</a>, in particular in the <a
836href="http://llvm.org/docs/">documentation</a> section. The web page also
Reid Spencer669ed452007-07-09 08:04:31 +0000[diff] [blame]837contains versions of the API documentation which is up-to-date with the
838Subversion version of the source code.
Misha Brukman109d9e82005-03-30 19:14:24 +0000[diff] [blame]839You can access versions of these documents specific to this release by going
840into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]841
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]842<p>If you have any questions or comments about LLVM, please feel free to contact
Chris Lattnerc463b272005-10-29 07:07:09 +0000[diff] [blame]843us via the <a href="http://llvm.org/docs/#maillist"> mailing
Chris Lattner5eccca42003-12-12 21:22:16 +0000[diff] [blame]844lists</a>.</p>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]845
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]846</div>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]847
848<!-- *********************************************************************** -->
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]849
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]850<hr>
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]851<address>
Misha Brukman38847d52003-12-21 22:53:21 +0000[diff] [blame]852 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]853 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
854 <a href="http://validator.w3.org/check/referer"><img
Chris Lattner8170c102008-02-10 08:18:42 +0000[diff] [blame]855 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a>
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]856
Chris Lattnerb4b0ce72007-05-18 00:44:29 +0000[diff] [blame]857 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]858 Last modified: $Date$
Misha Brukman2061e892003-11-22 01:23:39 +0000[diff] [blame]859</address>
Chris Lattner79c3fe12003-10-02 04:57:28 +0000[diff] [blame]860
Misha Brukman500bc302003-11-22 00:38:41 +0000[diff] [blame]861</body>
862</html>